MANKATO, Minn. -- In less than a year, Minnesota Vikings tackle Matt Kalil went from University of Southern California star to fourth-overall pick in the 2012 draft to Pro Bowl left tackle.

How can he improve on that?

"You need to be a lot more attentive than you are in college," Kalil said after Friday's practice. "Because you're going up against these vets, Julius Peppers and Clay Matthews and you have to be prepared. I think just becoming a student of the game is the biggest thing I've learned."

Instead of relying on his natural talent, Kalil buries his nose in game film -- studying opposing defensive ends across the league and not settling with the contentment of having the best running back in the NFL behind him.

"I know our offensive line coach Jeff Davidson is stressing to [Kalil], you really need to keep improving in our league," coach Leslie Frazier said. "There are guys studying him on tape just like he's studying defensive linemen. They're trying to come up with ways to have success against him. Matt wants to be the best left tackle in the NFL."

Despite fighting through knee and back issues and a pneumonia virus that cost him nearly 20 pounds midseason, Kalil played every snap at left tackle in his rookie campaign.

Kalil said he's back up to his playing weight, around 313 pounds, which is a shade heavier than he was last season.

"His weight hasn't changed a whole lot," Frazier said. "He's one of those guys that can play at a lean weight and be effective. He's unusual that way as an offensive lineman."

Kalil & Co. paved way for running back Adrian Peterson's 2,097-yard season last year, even though center John Sullivan had to have microfracture surgery on his knee in late January and tackle Phil Loadholt landed on the injury report a few times because of knee issues.

Kalil said the future is bright for an offensive line whose members are all younger than 30.